Mt Ruapehu crater lake could breach within two months | Rotorua News | Local News in Rotorua
Mt Ruapehu crater lake could breach within two months
Mt Ruapehu's 1995 eruption has led to the lahar formation now threatening to spill down the mountain.
By CHRIS BRAMWELL in Taupo
A lahar could occur on Mt Ruapehu as early as next month with the crater lake expected to reach full capacity within the next six weeks.
Department of Conservation conservancy advisory scientist, Harry Keys, said a lahar, or volcanic mud flow, is inevitable and while it's not known exactly when it will happen, the Ruapehu Crater lake is at 97 percent capacity and expected to reach 100 percent within two to six weeks.
The 1995/96 eruptions of Mt Ruapehu left several metres of rock fragments and particles around the rim of the crater, up to 15m in some places. At the lake's outlet above the Whangaehu Valley, the ash is about 7.5m high. As the lake water seeps through the debris the likelihood of a lahar increases and the higher the water seeps, the larger it will be.
About 60 lahars have come down the side of Ruapehu in the past 150 years. The threat of another has been growing as the level of the crater lake rises towards the rim threatening areas on the flanks of the mountain.
An embankment has been erected lower on the mountain to try and prevent a lahar spilling into the Waikato Stream and into Turangi.
Dr Keys said the chances of the bund breaching were less than 1 percent but if it were to happen the lahar would reach Turangi in four to eight hours.
Local and regional councils, police and other emergency services are working together in preparation for the event. The road bridge at Tangiwai is being lifted two metres, which is considered high enough to avoid lahar damage.
The nearby Tangiwai memorial will be removed and put into storage until after the event, when a safer location will be found.
A sophisticated early warning system is in place and the Department of Conservation estimates the lahar will take 90 to 120 minutes to reach the Tangiwai road and rail bridges, then 22 hours to make its way to the sea near Wanganui.
Police will be the first to respond and will block SH1 and SH49. Eight new police are being relocated to Waiouru on January 5 to be on standby.
A lahar could occur on Mt Ruapehu as early as next month with the crater lake expected to reach full capacity within the next six weeks.
Department of Conservation conservancy advisory scientist, Harry Keys, said a lahar, or volcanic mud flow, is inevitable and while it's not known exactly when it will happen, the Ruapehu Crater lake is at 97 percent capacity and expected to reach 100 percent within two to six weeks.
The 1995/96 eruptions of Mt Ruapehu left several metres of rock fragments and particles around the rim of the crater, up to 15m in some places. At the lake's outlet above the Whangaehu Valley, the ash is about 7.5m high. As the lake water seeps through the debris the likelihood of a lahar increases and the higher the water seeps, the larger it will be.
About 60 lahars have come down the side of Ruapehu in the past 150 years. The threat of another has been growing as the level of the crater lake rises towards the rim threatening areas on the flanks of the mountain.
An embankment has been erected lower on the mountain to try and prevent a lahar spilling into the Waikato Stream and into Turangi.
Dr Keys said the chances of the bund breaching were less than 1 percent but if it were to happen the lahar would reach Turangi in four to eight hours.
Local and regional councils, police and other emergency services are working together in preparation for the event. The road bridge at Tangiwai is being lifted two metres, which is considered high enough to avoid lahar damage.
The nearby Tangiwai memorial will be removed and put into storage until after the event, when a safer location will be found.
A sophisticated early warning system is in place and the Department of Conservation estimates the lahar will take 90 to 120 minutes to reach the Tangiwai road and rail bridges, then 22 hours to make its way to the sea near Wanganui.
Police will be the first to respond and will block SH1 and SH49. Eight new police are being relocated to Waiouru on January 5 to be on standby.
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